Polymeric acid containing gelatin interlayer for color photographic film

ABSTRACT

Color-photographic multi-layer materials having red-sensitized, green-sensitized, and blue-sensitized silver halide emulsion layers, each emulsion layer containing a color coupler, and gelatin interlayers for preventing undesirable coupling of developer oxidation products diffused in adjacent silver halide emulsion layers, contain in the gelatin interlayers 5 to 30 percent by weight of polyerms which contain acid groups. These interlayers are more effective in preventing the diffusion of developer oxidation products, as compared with pure gelatin interlayers. Thus it is possible to have interlayers of half the thickness of conventional interlayers. The materials have improved non-curling properties.

United States Patent [191 Lohmer POLYMERIC ACID CONTAINING GELATIN INTERLAYER FOR COLOR PHOTOGRAPHIC FILM [75] Inventor: Karl Lohmer, Leverkusen, Germany [73] Assignee: Agfa-Gevaert Aktiengesellschaft,

Leverkusen, Germany [22] Filed: May 10, 1972 [21] Appl. No.: 252,025

[30] Foreign Application Priority Data OTHER PUBLICATIONS Chem. Abstr. 52, 18042, 11/10/58.

[4 Oct. 16, 1973 Primary Examiner-Norman G. Torchin Assistant ExaminerR. L. Schilling Attorney-Arthur G. Connolly et al.

[5 7] ABSTRACT Color-photographic multi-layer materials having redsensitized, green-sensitized, and blue-sensitized silver halide emulsion layers, each emulsion layer containing a color coupler, and gelatin interlayers for preventing undesirable coupling of developer oxidation products diffused in adjacent silver halide emulsion layers, contain in the gelatin interlayers 5 to 30 percent by weight of polyerms which contain acid groups. These interlayers are more effective in preventing the diffusion of developer oxidation products, as compared with pure gelatin interlayers. Thus it is possible to have interlayers of half the thickness of conventional interlayers. The materials have improved non-curling properties.

2 Claims, No Drawings POLYMERIC ACID CONTAINING GELATIN INTERLAYER FOR COLOR PHOTOGRAPHIC FILM This invention relates to a multi-layer colorphotographic material in which polymers containing acid groups are added to the gelatin intermediate layers arranged between the differently sensitized silver halide emulsion layers in order to improve the noncurling properties of the material.

It is known that colored images can be produced using a multi-layer color-photographic material comprising at least one red-sensitized silver halide emulsion layer containing a cyan-forming coupler, a greensensitized silver halide emulsion layer containing a magenta-forming coupler and a blue-sensitive silver halide emulsion layer containing a yellow-forming coupler. To produce the individual partial color images, the differently sensitized silver halide emulsion layers are usually separated from one another by gelatin intermediate layers which can, if desired also contain filter dyes. The main object of these gelatin intermediate layers is to prevent or hinder oxidation products of the color developer formed in a layer during development diffusing into other coupler-containing layers where they could couple with the couplers in these other layers. These intermediate layers thus prevent the formation of undesirable dyes in the other layers. This effect of formation of undesirable dyes by coupling of diffused developer oxidation product is referred to herein as co-coupling. It is obvious that, in order completely to suppress this troublesome co-coupling the intermediate layers must have a certain thickness which can vary between one and several um, depending upon the particular type of color coupler and color developer used. The intermediate layer must be sufficiently thick to ensure that color developer oxidation products which are capable of coupling are destroyed by hydrolysis before reaching an adjacent coupler-containing layer.

In conditions of high relative humidity gelatin expands to a greater extent than the layer support and conversely in low relative humidity the gelatin shrinks to a greater extent than the layer support. As a result of this the color-photographic material after processing shows a troublesome tendency to curl up, depending upon the relative humidity. In conventional material, this tendency can only be controlled to a limited extent by varying (i.e., by reducing) the layer thicknesses. A

. reduction in the thickness ofthe emulsion layers generally results in a loss of sensitivity and color density, and a reduction of the thickness of an intermediate layer is out of the question on account of the danger of unwanted co-coupling which it would involve. Attempts have already been made to prevent color developer oxidation products from diffusing into other couplercontaining silver halide emuslion layers by incorporating into the intermediate layer diffusion-resistant colorless reducing agents which reduce the oxidized color developer diffusing through. Another method of eliminating co-coupling is to incorporate so-called white couplers into the gelatin intermediate layer in such a way as to prevent diffusion. These white couplers react with the difussing developer oxidation product to form colorless compounds and thus prevent undersirable dye formation in the coupler-containing photographic layer. Both processes involve technical disadvantages.

In the first case reducing agents have undesirable side effects upon the photographic layer. In the second it is found that white couplers only produce the required effect when used in quantities which adversely affect the fogging value.

It is an object of the present invention to produce a color-photographic material with imporved noncurling properties, which will lie flat. The invention seeks to provide a material which shows little or no tendency to curl irrespective of the relative humidity.

It has now been found that the thicknesses of the gelatin intermediate layers can be reduced and hence the non-curling properties of multi-layer colour photographic materials can be improved by replacing some of the gelatin of the gelatin intermediate layers arranged between the differently sensitised silver halide emulsion layers to prevent co-coupling, by polymers containing acid groups.

Accordingly, the invention relates to a photosensitive color-photographic material which comprises at least one red-sensitized silver halide emulsion layer containing a cyan-forming coupler, a green-sensitized silver halide emulsion layer containing a magentadorming coupler and a blue-sensitive silver halide eulsion layer containing a yellow-forming coupler with gelatin intermediate layers between the aforementioned silver halide emulsion layers. The material is characterized by the fact that at least one intermediate layer contains a polymer containing acid groups in a quantity of from 5 to 30 percent by weight and preferably in a quantity of from 15 to 25 percent by weight, based on the gelatin.

In the context of the invention, polymers containing acid groups are polymers compatible with gelatin which are diffusion-fast in gelatin layers and, hence whose acid groups are present in the form of diffusionresistant anions at the pI-I-value at which color development is carried out. Examples of polymers containing acid groups include polymers and copolymers of acrylic acid, copolymers of maleic acid, styrene sulfonic acid, and cellulose derivatives containing acid groups.

Since the advantageous results apparently depend on the presence of acid groups in the diffusionfast polymer, the particular composition and the molecular weight of the polymer used seems to be uncritical, as long as the content of the acid groups per monomeric unit is sufficiently high. To be particularly suitable according to the invention the polymers and copolymers of acrylic acid and the copolymers of maleic acid contain on an average 0.2 to l carboxylic acid groups per monomeric unit, the polystyrene sulfonic acid contains on an average 0.5 to l sulfonic acid group per styrene unit. The carboxymethyl cellulose contains 0.5 'to .lcarboxylic group per glucose unit and the cellulo'sesulfat contains 1 2 sulfuric acid groups per glucose unit.

The copolymers of acrylic acid and maleic acid may contain other comonomeric units for example selected from the group consisting of alkylvinyl ethers having up to four carbon atoms in the alkyl group, vinylesters such as vinyl acetate or vinyl propionate, vinyl alkohol, styrene, alkyl acrylates and alkyl methacrylates having up to four carbon atoms in the alkyl group, and acrylamide. Preferred copolymers of acrylic acid contain 20 to 50 mols percent of acrylic acid and 50 to mols percent of ethyl acrylate. A preferred copolymer of maleic acid contains about 50 mols percent of maleic acid and about 50 mols percent of styrene.

The carboxymethylcellulose preferably has a viscosity of 800 cps (2 percent aqueous solution, C; this corresponds to a molekular weight 40,000 200,000) and the cellulose sulfate preferably has a viscosity of 12 80 cps. (2 percent aqueous solution, 25). Standard carboxy-methyl cellulose and cellulose sulfate have proved to be particularly suitable.

it was surprisingly found in the color-photographic materials produced in accordance with the invention that the layer thicknesses of the intermediate layers required for color separation can be significantly reduced by comparison with the pure gelatin layers normally used without any danger of troublesome co-coupling occurring.

The negatively charged ion groups evidently act as a barrier to the diffusing color developer oxidation product which probably migrates in the form of a positively charged immonium ion, thus preventing its diffusion. The separating effect obtained with the intermediate layers according to the invention is equal to-that obtained with pure gelatin layers of about twice the layer thickness. This is a considerable advantage because better mechanical properties are obtained with lower layer thicknesses. The reduction in the layer thicknesses that is possible in this way evidently makes a considerable contribution towards improving the noncurling properties of color-photographic materials as well. The ability of the polymers containing acid groups according to the invention to swell rapidly with water may possibly also have a favourable effect upon the non-curling properties. The layer thickness of the intermediate layers according to the invention is between 1 and 1.5 pm. Conventional gelatin intermediate layers are considerably thicker, their layer thickness amount-- ing to about 2 am.

The aforementioned polymers containing acid groups can be added to the gelatin either by mixing the dry gelatin with the powdered polymer and dissolving the resulting mixture in water, or by preparing separate solutions in water of the gelatin and of the polymer containing acid groups and subsequently mixing the resulting solutions in the required ratio.

Suitable layer supports for the material according to theinven-tion include the usual supports such as, for example, baryta paper, hydrophibized paper such as polyethylene-lined paper, or films of polyethylene terephthalate, cellulose ester, polycarbonat or other film forming materials.

Preventing the difussion of oxidized color developer from a layer containing color coupler into an adjacent layer during color development by the incorporation of polymers which are present as negatively charged polyions at the pH-value of the developer, in accordance with the invention, is of course not confined to a certain layer support or certain color developers of color couplers, but instead applies generally to multi-layer color-photographic systems which are developed with color developers of the phenylene diamine series.

The process according to the invention is illustrated by the following Examples.

EXAMPLE posed to a corona discharge:

l. A red-sensitized silver bromide gelatin emulsion layer containing a hydrophilic cyan coupler;

2. An intermediate layer of a 4 percent aqueous gelatin solution containing 1.9 g of gelatin per square metre (Layer thickness: 1.9 pm);

3. A green-sensitized silver bromide gelatin layer containing a hydrophilic magenta coupler;

4. The same gelatin intermediate layer as layer 2;

5. A blue-sensitive silver halide gelatin containing a hydrophilic yellow coupler; and

6. a protective layer of the same composition as layer Processing A step wedge is exposed on this material behind selective blue, green and red filters and then colourdeveioped in the usual way.

Color wedges are obtained in which only one of the three color layers was developed in each case due to the selective exposure. Comparison of these partial color images from the three-layer material with the corresponding color wedge produced from a single casting does not show any appreciable deviations in color attributable to co-coupling in the three-layer material. Sample B A material identical with that described above is prepared in another test. However, the gelatin separating layers are cast more thinly so that only 1.1 g of gelatin is applied per square metre (layer thickness 1.1. am).

In this material, the colors of the partial color images obtained from the three-layer material are no longer consistent with those of the corresponding single layer material despite of similar processing. They are heavily contaminated by color components formed through cocoupling from the adjoining unexposed-color layers and hence are less pure than in comparison sample A. Sample C This material is similar in structure to samples A and B, except that the following casting solution is used in stead of the 4 percent gelatin solution to apply the intermediate layers:

2 g of polystyrene sulfonic acid (molecular weight 3,000 to 4,000) in 500 ml of water are adjusted with sodium hydroxide to a pH-value of 6.5. 500 ml of the 4 percent of gelatin solution are then added. The application is adjusted in such a way that 1.2 g of solids are applied per square metre (layer thickness 1.2 pm).

The material is processed as described above. When photographically tested for color purity, this material is as good in its color reproduction as comparison sample A despite the thin intermediate layers.

Sample D 7 in the intermediate layers, the polystyrene sulfonic acid is replaced by 5 g of a copolymer of 25 percent of acrylic acid, 35 percent of ethyacrylate and 40 percent of ethylmethacrylate, the structure of the material being otherwise the same. The application amounts to 1.1 g/m (layer thickness 1.1 pm). This material as well shows the same excellent color separation as sample A. Sample E Intermediate layers are applied from the following casting solution (the structure of the material being otherwise the same):

2 g of a copolymer of styrene and maleic acid (1 l) are neutralized in 500 ml of water and added to 500 ml of the 4 percent gelatin solution.

The application is again adjusted to a solids of 1.2 g/m (layer thickness 1.2 pm). This material is also equal in its color separation to sample A.

Sample F The following casting solution is used for the intermediate layers:

2 g of polyacrylic acid are adjusted to pH 6.5 with sodium hydroxide in 500 ml of water and added to 500 ml of the 4 percent gelatin solution. The application is controlled in such a way that 1.0 g of solids are applied per square metre (layer thickness 1.0 pm). Despite the thinness of this intermediate layer, photographic testing shows that co-coupling is suppressed just as effectively as in sample A.

Sample G Casting solution for the intermediate layers:

4 g of sodium carboxymethyl cellulose (viscosity 25 cps of the 3 percent aqueous solution at 25C) are dissolved in 500 ml of water and mixed with 500 ml of 4 percent gelatin solution. The application is regulated in such a way that 1.0 g of solids is applied per square metre (layer thickness 1.0 pm). Color separations again corresponds to sample A.

Sample H In another test, 4 g of cellulose sulfate (viscosity of the 2 percent aqueous solution cps at 25C) are dissolved and added to 500 ml of the 4 percent gelatin solution. The casting solution thus obtained is applied as an intermediate layer. The application is regulated in such a way that 1.0 g of solids is applied per square metre (layer thickness 1.0 pm). This material is also equal in its color separation to sample A.

After processing, samples A to H show distinct differences in their curling behaviour under different climatic conditions, as shown in the following Table.

30% relative 50% relative relative humidity humidity humidity Sample A 4/8 2/8 0/8 Test B 2.5/8 l/B 0/8 Tests C through H 2/8 l/8 0/8 The curling values under the particular climatic conditions are given in eighths, 8/8 meaning that the test specimen curls up into a cylinder full circle 8/8).

I claim:

1. In a photosensitive color-photographic material comprising at least one red-sensitized silver halide emulsion layer containing a cyan-forming coupler, a green-sensitized silver halide emulsion containing a magenta-forming coupler and a blue-sensitive silver emulsion layer containing a yellow-forming coupler, and having gelatin intermediate layers arranged between the aforementioned silver halide emulsion layers, the improvement according to which at least one gelatin intermediate layer contains a polymer containing acid groups in a quantity of from 5 to 30 percent by weight based on the gelatin.

2. The combination of claim 1, wherein the polymer containing acid groups is selected from the group consisting of polymers and copolymers of acrylic acid and copolymers of maleic acid containing 0.2 to l carboxylic acid groups per monomeric unit, poly styrene sulfonic acid containing 0.5 to 1 sulfonic acid groups per styrene unit, carboxy methyl cellulose containing 0.5 to 1 carboxylic acid groups per glucose unit, and cellulose sulfate containing 1 to 2 sulfuric acid groups per glucose unit. 

2. The combination of claim 1, wherein the polymer containing acid groups is selected from the group consisting of polymers and copolymers of acrylic acid and copolymers of maleic acid containing 0.2 to 1 carboxylic acid groups per monomeric unit, poly styrene sulfonic acid containing 0.5 to 1 sulfonic acid groups per styrene unit, carboxy methyl cellulose containing 0.5 to 1 carboxylic acid groups per glucose unit, and cellulose sulfate containing 1 to 2 sulfuric acid groups per glucose unit. 